WASP-4 transit timing variation from a comprehensive set of 129 transits
Abstract
We homogeneously reanalyse 124 transit light curves for the WASP-4 b hot Jupiter. This set involved new observations secured in 2019 and nearly all observations mentioned in the literature, including high-accuracy GEMINI/GMOS transmission spectroscopy of 2011-2014 and TESS observations of 2018. The analysis confirmed a nonlinear TTV trend with P/| P| (17-30) Myr (1-sigma range), implying only half of the initial decay rate estimation. The trend significance is at least 3.4-sigma in the agressively conservative treatment. Possible radial acceleration due to unseen companions is not revealed in Doppler data covering seven years 2007-2014, and radial acceleration of -15 m s-1yr-1 reported in a recent preprint by another team is not confirmed. If present, it is a very nonlinear RV variation. Assuming that the entire TTV is tidal in nature, the tidal quality factor Q' (4.5-8.5)· 104 does not reveal a convincing disagreement with available theory predictions.